1. Field
The present application relates to amplifiers used in envelope tracking mode. In particular, the present disclosure relates to optimization methods for amplifiers with variable supply power.
2. Description of Related Art
Although methods using amplifiers in a non-linear way (e.g., compression region) can exhibit higher power efficiency than conventional linear methods, until recently nonlinear methods were inappropriate for usage in applications wherein utmost fidelity in the amplification of the input radio frequency (RF) signal was required, especially when the RF signal contains large amplitude dynamic range (e.g., high peak-to-average power ratio) due to associated modulation scheme (e.g. WCMDA, LTE). A technique known as envelope tracking was developed that allows usage of power amplifiers operating in the compression region with excellent linearity in response while maintaining benefits of power efficiency associated with this type of operation. This technique dynamically adjusts the supply power to the power amplifier in a manner that roughly follows the time varying envelope of the RF signal fed to the amplifier, and forcing the amplifier to mostly operate in the compression region.